1. Field of the Invention
This invention is concerned with improvements in face type seals and more particularly with incorporation of the face type seals into a unitized housing.
2. Description of the Prior Art
Face type seals, also called rotary end face mechanical seals, generally have a primary seal comprised of a first and a second relatively stiff primary sealing ring and a pair of secondary sealing or annular resistant rings generally of elastomeric material. The sealing rings have abutting mating faces or surfaces that are highly polished hard surfaced metallic faces which are lapped to extremely flat superfine finish profiles. The secondary sealing members are positioned between adjacent housings and the back sides of the primary sealing rings. One housing is generally a stationary housing, for instance an axle housing, while the other housing is usually an internal bore in a rotating member, for instance a wheel hub.
The annular resilient rings serve a dual function. Firstly the resilient rings provide a loading force on the back side of the primary sealing rings to ensure good face to face contact and secondly the resilient rings provide a seal that prevents fluid flow from one side of the resilient rings to the other, either between one of the housing/resilient ring margins or one of the sealing ring/resilient ring margins.
U.S. Pat. Nos. 3,940,154 to Olsson and 3,241,843 to Hatch show typical face type seals that are different from this invention but set forth the state of the art.
Prior art seals have proven themselves effective in severe duty environments where the seal is constantly exposed to dirt, grit and dust. Hence these face type seals lend themselves particularly well to off highway construction equipment.
The need to maintain the superfine finish on the mating faces of the sealing rings is critical to good seal performance and life expectancy. It has been found that once the sealing rings and the accompanying resilient rings are properly installed the sealing rings will perform well, however, if contamination is present on the superfine finish surfaces of the sealing rings at the time of installation then the seal will fail prematurely.
At least one solution to preventing the inclusion of dirt during assembly is the use of a cellulose band, shown in the above mentioned Hatch patent, that is shrunk around the outer periphery of the sealing rings at the time of manufacture. Subsequent to the installation of the joined sealing rings the normal rotation of the adjoining housings will break the band which is then disintegrated.
The difficulty experienced with prior art face type sealing rings is that there are two basic component sets each set including a primary sealing ring and an annular resilient ring. These two basic component sets eventually are separated, either when the host structure is overhauled or even earlier when the machine is being assembled (if the prior art patented band is not used). This separation of the two basic component sets provides a chance for foreign matter to get between the mating faces and ruin the seal.
Another difficulty with prior art face type seal sets is that as they are independently installed in the host housings there is a chance of misalignment between them that will generate unequal loading around the faces of the mating sealing rings. This unequal loading may also be detrimental to the life expectancy of the seal.
It is among the objects of this invention to provide a face type seal that has a unifying multi-part enclosure for containing the two basic component sets.
Another object of the invention is to provide a face type seal that has all its parts contained in a single unitized component.
Also an object is to provide a unitized face type seal that, as a single component, is constructed so as to prevent the inclusion of contamination between the sealing faces prior to installation.
Another object is to provide a face type seal that is arranged as a unitized component so as to ensure perfect alignment between the seal faces before, during and after installation.
A further object of this invention is to provide a face type seal having an installation location guide flange integral with the unitized face seal component.
These and other objects and advantages of this invention will be apparent from the accompanying description and drawing figures.